1. Field of the Invention
The present invention consists in a method of fabricating submicron suspended objects and in microelectronic components fabricated by the method. The invention also relates to determining at least one property of the objects or the materials constituting them.
2. Description of the Prior Art
In the field of microelectronics, increasingly smaller microcircuits are used. Apart from reducing their overall size, miniaturization reduces the electrical power consumption and increases the speed of the circuits. The technologies currently used in microelectronics produce microcircuit elements such as component connections with submicron dimensions. In the present application, the expressions “submicron object” and “nanometer object” refer to objects having dimensions less than a few microns (micrometers (μm)), generally of the order of a few hundred nanometers (for example from 50 to 300 nanometers), except for one dimension (generally their length) which can exceed a few microns, although this is not necessarily the case. For example, a submicron object of rectangular parallelepiped shape will have a width and a height generally less than 1 μm, of the order of a few hundred nanometers, and a length that can exceed a few microns, while an object of cylindrical shape will have a cross section diameter less than 1 μm, for example a few hundred nanometers, and a length that may exceed several microns.
Because of their small size, these submicron objects are produced on a support, generally a semiconductor, or on an insulative layer, for example a layer of silicon nitride or oxide, itself deposited on a support. Although their electrical properties can be determined relatively easily, until now it has not been possible to determine mechanical properties of these objects or the materials constituting them in a satisfactory manner. For example, the method described by Michael D. Uchic, Dennis M. Dimiduk, Jeffrey N. Florando and William D. Dix in their paper “Sample dimensions influence strength and crystal plasticity” published Aug. 13, 2004 in Science, Vol. 305, pages 986-989, consists in using a focused ion beam (FIB) to cut a submicron cylinder having a diameter from 100 to 200 nm in a thin layer of material whose mechanical properties are to be determined. An indentation point is pressed onto the top of the cylinder and the displacement of the point as a function of the applied force is measured. This technique has the drawback that it does not really represent the characteristics of the material on the submicron scale since the cylinder tested has not been fabricated with submicron dimensions but cut from a layer of much greater size, for example of the order of 1 cm. At submicron dimensions, new physical phenomena arise that do not exist on a larger scale. This results in different mechanical properties. It is important to characterize submicron objects mechanically and electrically in order to adjust their fabrication methods, for example the composition of the material or materials from which the objects are fabricated, the interfacing of the components or the methods of cleaning and annealing the components. Knowing the mechanical properties of submicron objects enables the design of microelectronic methods of fabricating the objects, such as microchips and other microelectronic components, and improves the reliability of those components and microcircuits.
The present invention offers a solution to the above problem by proposing a method of fabricating submicron suspended objects. The characterization of the mechanical and electrical properties of the objects is a true representation of their properties on the submicron scale because the objects are fabricated at that scale and no longer rest at least in part on a support. The electrical insulation of the objects is perfect as they are surrounded by air.